1. Field of the invention.
The present invention relates to tire dismounting apparatus and more particularly to a device for unseating the bead of a pneumatic tire.
Large size tires and wheel rims, such as those presently used on transport trucks, and the like, because of their size and mass are difficult to handle and remove the tire from the metal wheel rim. The side walls of the tire at their interior margins have beads, which tightly embrace cooperating bead seats formed on or forming a part of the rim. After the tire has been in use even for a short period of time these seals are extremely difficult to break.
2. Description of the prior art.
Tire changing machines or apparatus presently in use are generally designed for passenger car size wheels, such as U.S. Pat. Nos. 2,842,191 and 3,905,413, and on account of the mass of large size truck tires are not adaptable for use in dismounting such truck tires. Another U.S. Pat. No. 3,033,268, discloses an apparatus for holding a truck tire and wheel and rotating it about its axis which includes a shoe movable toward and away from a relatively small arc of the tire side wall adjacent the wheel rim for progressively breaking the tire bead seal. Still another U.S. Pat. No. 3,865,172 discloses an apparatus for breaking the bead of relatively large size tires, such as are used on earth movers, in which a tire bead breaking finger is power driven against the tire bead at one side of the tire with an identical finger on the opposite tire bead serving as a backstop.
The principal disadvantage of apparatus, such as disclosed by these patents for progressively breaking the tire bead, resides in the tire bead being moved toward a resealing position on the bead seat when the bead breaking members are moved to another position adjacent the wheel rim and near the previously loosened tire bead area. Other giant size tire bead breaking apparatus is disclosed by U.S. Pat. No. 3,972,363 which discloses an overhead track assembly for supporting a hoist for handling the tire and wheel and manually positioning circumferentially spaced tire side wall engaging members subsequently moved against the tire side wall by a pressure cylinder connected therewith by having its piston rod extending through the wheel center and between backing members.
This invention is an improvement over the prior art by providing a rigid open frame into which a wheel rim mounted truck tire, or the like, may be rolled and supported against lateral movement and in which a pressure cylinder, coaxial with the tire and wheel, moves a tire side wall engaging endless ring toward the tire side wall for unseating the tire bead.